The present invention relates to a machine control device to move a control object machine to a target position and halt the machine, and relates to a machine control device which suppresses vibration of the control object machine due to inertial forces at the time of halting.
FIG. 20 is a schematic conceptual diagram of a control object machine. The machine 10 includes a heavy article 11, arm 12, sliding movement portion 13, slide rail portion 14, feed screw 15, coupling 16, motor 17, and any one of the machine control devices 20, 40, 43 to 48, and 50 to 54. Of these, the control object machine comprises the heavy article 11, arm 12, sliding movement portion 13, slide rail portion 14, feed screw 15, and coupling 16.
In FIG. 20, the slide rail portion 14 constrains the sliding movement portion 13 to move only in the right-left movement directions in the figure. And, the contact portions of the slide rail portion 14 and the sliding movement portion 13 have low friction, so that the sliding movement portion 13 can move smoothly over the slide rail portion 14. The output shaft of the motor 17 is connected to the feed screw 15 via the coupling 16, and this feed screw 15 is screwed into a screw interior, not shown, mounted on the sliding movement portion 13. That is, through rotational driving of the feed screw 15 by the motor 17, the sliding movement portion 13 moves in the right and left directions in the figure according to position control operation by the machine control device.
A long arm 12 is mounted on the sliding movement portion 13 which is positioned-controlled in this way, and a heavy article 11 is mounted on the end of this arm 12. Hence through position control of the sliding movement portion 13, the position of the heavy article 11 at the end of the arm 12 is also controlled.
For the configuration shown in FIG. 20, it is known that even when the sliding movement portion 13 is halted at the target position, the heavy article 11 at the end of the arm 12 causes the arm 12 to flex due to its own inertial force, advancing further than the instructed position, so that halting may not be immediate and vibration may occur even after the sliding movement portion 13 has halted at the target position.
FIG. 21 shows the circuit configuration of a conventional machine control device 20 including functions to suppress the above-described vibration phenomenon; this circuit configuration is disclosed in Japanese Patent Application Laid-open No. 2003-76426. The machine control device 20 comprises a position regulator 21, velocity regulator 22, torque regulator 23, position instruction unit 24, correction unit 25, and adder 26.
In FIG. 21, in the position regulator 21, a regulation operation is performed such that the position detection value from a motor encoder 17a mounted on the motor 17 matches the position instruction value of an instruction; the output is sent as a velocity instruction value to the velocity regulator 22. In the velocity regulator 22, a regulation operation is performed such that the velocity detection value from the motor encoder 17a matches the velocity instruction value; the output is sent as a torque instruction value to the torque regulator 23.
In the torque regulator 23, control is executed to drive the motor 17 according to the torque instruction value, via an inverter incorporated within the torque regulator 23, to move the sliding movement portion 13 of the machine 10 to a prescribed position, and to halt the machine.
In the position instruction unit 24, a position instruction value is output to move the sliding movement portion 13 to the target position; in the correction unit 25, the second derivative value of the position instruction value (the acceleration instruction value) is multiplied by a prescribed gain to determine a correction amount, and this correction amount is added to the position instruction value by the adder 26; the addition value is sent to the position regulator 21 as the new position instruction value.
That is, in the machine control device 20 shown in FIG. 21, a transfer function based on the above-described correction unit 25 and adder 26 acts so as to cancel the vibration element component of the transfer function derived from the spring constant of the arm 12 and the mass of the heavy article 11, so as to suppress the above-described vibration phenomenon in the control object machine.
In the conventional machine control device 20 shown in FIG. 21, in order to quicken the response to a position instruction value, the proportional gain must be further increased in regulating operation of the position regulator 21; but when an abrupt disturbing torque occurs in the control object machine or at other times, if the proportional gain is made too great, there is the problem that vibration phenomena of the control object machine cannot be adequately suppressed.
Further, when the arm of the control object machine is long and the rigidity thereof is low, or when the heavy article is heavy and the position thereof is high, there has been the problem that in the circuit configuration of the conventional machine control device 20, vibration phenomena of the control object machine cannot adequately be suppressed.
In view of the above, it would be desirable to provide a machine control device which resolves the above-described problem.